The Complete Rules of Omaha

Omaha, or correctly expressed Omaha Hi, is played only for the highest hand, and therefore resembles Texas Hold'em. The decisive difference is that in Omaha the starting hand consists of four face down cards, instead of two cards as in Hold'em. In Omaha, the final hand is composed of exactly two (no more or less) of the private hole cards together with three of the community cards on board. Otherwise, the rules and the course of the game are the same as in Texas Hold'em.

In Hold'em, your two pocket cards can make only one starting combination. In Omaha, the four hole cards form six different combinations. Therefore, in Omaha there are more options, and the winning hands tend to be stronger. In Hold'em, two pair is regularly good enough. In Omaha, you may need a flush or a straight. In Hold'em, any flush or straight is a strong hand. In Omaha you may need the highest possible combination, and a straight draw to the lower end, for example, is a much more serious mistake.

In Omaha H/L, also called for Omaha 8 or Better, the pot is split between the high and the low hand. A high hand will always exist, a low hand is sometimes not to be found. In that case, the high hand wins the whole pot.

 
A low hand is composed of five unpaired cards from A to 8. The ace is the lowest card. Two of the cards have to come from the pocket hand and three from the board, and they can't make a pair. Consequently, the best low hand is A-2-3-4-5. The ranking is determined by the highest card, if they are the same, the next highest etc. In other words, 3-4-5-6-7 is better (lower) than  A-2-3-4-8. A possible flush or straight won't make any difference in this context. On the other side, a flush or a straight can form the high hand, and the same player can claim the whole pot with the same cards. The high and the low hands can also be made using different cards.